We have produced mice that do not make mesothelin and are comparing them with normal mice to determine if various types of cancer will grow in the peritoneal cavity of these mice, where mesothelin is present on the mesothelial cells lining the peritoneal cavity of the normal mice. We have crossed these mice with immuno-deficient mice to make meso-/-, nu/nu mice to allow human cancer cells to grow in the peritoneal cavity of the mice. We have implanted mesothelin negative SHIN 3 cells into the peritoneal cavity of these mice and find they grow more slowly than in mesothelin expressing mice. We have also found that injecting these mice with MPF enhances the growth rate of these tumors. We are studying the mechanism of this effect.